Soay sheep are a primitive breed of sheep (Ovis aries ) descended from a population of feral sheep on the island of Soay. They are similar to the Mediterranean mouflon and, although their origins are uncertain, they are believed to have been deposited upon the island, part of the Saint Kilda archipelago, by Vikings. They are much smaller than modern domesticated sheep but are believed to be hardier. A number of Soay sheep were translocated from Soay to the island of Hirta by the Marquis of Bute in the 1930s, after the human population was evacuated. The population is unmanaged and has been the subject of scientific study since the 1950s. The population make an ideal model subject for scientists researching evolution, population dynamics and demography because the population is unmanaged, closed (no emigration or immigration) and has no significant competitors or predators.